Another point to consider is that unlimited votes would make personality voting, currently something I don't consider much of an issue, a very serious problem. With nothing stopping you from voting 400 or even 40,000 times in a day, you would only have to create a couple accounts to downvote someone into oblivion. With the current system, substantial abuse that puts the site's worth in jeopardy is not possible.

Makeshifts last the longest.